Senior Back-End Developer

About The Company
Hercle is a fast-growing fintech building institutional-grade infrastructure that bridges fiat, stablecoins, and digital assets, enabling cross-border payments and banking infrastructure for global trade.

Serving over 200 clients globally, Hercle provides banks, brokers, payment service providers, fintechs, commodity traders, corporate treasuries, and other NBFIs with seamless solutions for cross-border payments and treasury management.

Working at Hercle
We're a lean, flat team where ideas matter more than titles and everyone gets real responsibility from day one. You'll solve complex problems at the intersection of global finance and digital assets, for some of the world's largest institutions and corporates. If you're curious, driven and excited to shape how money moves globally, we'd love to meet you.

About The Role
We're looking for a Senior Back-End Developer to join our Payments squad, which owns Hercle's money journeys end to end. The goal: one unified way to move money from A to B (deposits, withdrawals, transfers, transfer-outs and rebalancing), whoever is sending and whoever holds the funds.

Key Responsibilities

Design and build a scalable, event-driven payment orchestration engine for deposits, withdrawals, transfers and rebalancing

Implement state machines, idempotency, retries and compensation so every money movement is safe, traceable and recoverable

Integrate orchestration with account data, provider adapters (banks, custodians, exchanges) and the core ledger

Build and operate the job fleet that automates rebalancing and recurring flows, with strong monitoring and alerting

Work with product, Operations and banking infrastructure clients to remove manual steps and improve journey success rate and speed

Write clean, documented code, review peers' work, fix bottlenecks and bugs, and improve CI/CD

How We Build
Every squad works on our two C# code bases: the Execution API, the client-facing gateway exposing documented REST and real-time WebSocket (SignalR) APIs, and the Back Office API, used daily by Operations, Compliance and the trading desk. Behind them sits a fleet of domain microservices and provider integrations.

.NET 10 microservices over gRPC; event-driven internals with CQRS, domain events and background jobs

AWS throughout: EKS, DynamoDB (in-memory caches on the hot path), Cognito, OpenSearch, S3

Azure DevOps CI/CD, with integration tests run against real deployed environments

AI-first engineering: agents write and refactor code, review every PR and help investigate incidents

What You Will Work On
You own every money movement on the platform, from the client request to the provider confirmation and the ledger entry.

Deposit, withdrawal and transfer flows over WebSocket and REST, incl. payees and crypto addresses

Banking orchestration: one canonical model routing to banks, crypto custodians and Lightning

The balance pipeline: reservations, a ledger entry per change, compensation on provider failure

Async provider states (webhooks, retries, idempotency): no payment lost or executed twice

Operations flows: approvals, rebalancing across exchanges and accounts, scheduled jobs

Requirements

Bachelor's degree in Computer Science, Engineering or a related technical field

5+ years building back-end systems in a strongly typed language (e.g. C#/.NET, Java, Kotlin, Go)

Strong grasp of OOP, design patterns, distributed systems, concurrency, multithreading and performance optimisation

Experience with SQL and NoSQL databases, CI/CD, Git and testing frameworks

Strong problem-solving, attention to detail and ownership in a fast-paced environment

Daily, hands-on use of AI coding agents on production work (not just autocomplete), with the judgement to give them the right context and to review and own what they produce

Fluent written and spoken English

Nice to have

Strong C#/.NET experience

Familiarity with payment rails (SEPA, SWIFT, Faster Payments, on-chain and Lightning) and blockchain transactions, wallets and stablecoin transfers

Experience with orchestration patterns: sagas, outbox, compensation across several external providers, message brokers (e.g. Kafka, RabbitMQ)

Knowledge of double-entry l